The invention relates to electrical wiring devices and more particularly to duplex electrical receptacles and housings therefor which are suitable for mounting in conventional wall boxes.
Duplex electrical receptacles may be categorized as either general purpose or self-contained receptacles. As is well known, general purpose duplex receptacles are typically designed to have two sets of two or three female contacts in each set, depending upon whether the receptacle is of the ungrounded or the grounded type. In the grounded type of receptacle, electrical connections are made to the ground terminals as well as to the power and neutral terminals. In ungrounded receptacles, ground terminals are eliminated.
General purpose receptacles usually have both a single and a split (or dual) circuit operating capability. Usually, the split circuit mode is used when each set of contacts is to be fed electrical power from independent circuit sources. The single circuit mode is usually used when it is desired that the electrical current supplied to the one set of contacts also feed-through to the other set of contacts and possibly to more downstream connected wiring devices coupled into the receptacle circuit.
A slotted tab provided in the electrical structure joining the different sets of contacts may be broken off by a screwdriver blade tip inserted into the tab or by pliers to convert the receptacle from the single circuit mode to a split (or dual) circuit mode. With the receptacle connected in a split circuit mode, both sets of contacts can be operated independently of each other. For example, one-half of the receptacle can be selectively energized by operation of an electrical wall switch connected to only the one set of contacts mounted in that one-half while the other set of contacts mounted in the other half of the receptacle can be energized continuously from conductors connected to the source of circuit power or through an upstream wiring device, such as another receptacle.
Self-contained receptacles as compared to general purpose receptacles, are designed to have only a feed-through or single circuit capability but do not have a split circuit capability. Moreover, because of their construction, fire code requirements presently limit installation and usage of self-contained devices to the first two levels of a building or other structure. The receptacles are primarily designed for assembly with special purpose assembly tools and usually can only be connected with non-metallic, sheathed cable. Because of their different-than-standard usage sizes and special mounting requirements, self-contained receptacles are usually not interchangeable with the aforedescribed general purpose receptacles. Moreover, the design of the housings of self-contained receptacles does not permit them to be mounted in the general purpose type of metallic wall boxes which are designed to accommodate various types of general purpose receptacles.
The insulated conductors may be connected to terminals of the self-contained receptacles by use of the so-called "insulation-displacement" technique. This technique typically involves pushing a conductor into a terminal slot such that the slot penetrates or cuts through the conductor insulation sufficiently to make electrical contact with the underlying conductor wire. One way to do this is by use of a special parts-clamping tool, resembling a large hand pliers. Proper operation of this tool requires a modicum of skill and dexterity by the installer and convenient access to the wire and terminal slots. The insulation-displacement technique is a wire connecting technique which has been used with male and female electrical contacts in single circuit types of wiring devices, as described in my U.S. Pat. No. 4,196,956, assigned to the same assignee as this application.
The invention constructed in accordance with this invention is a receptacle and a housing therefor of the general purpose type with single and split circuit capability. The receptacle is adapted for mounting in standard or general purpose wall or floor boxes and may be easily and readily wired to associated electrical conductors by forcing the conductors into terminals with the side covers of the receptacle which side covers then complete the enclosure of the receptacle housing.
More specifically, a receptacle made in accordance with the invention is virtually independent of the quality of workmanship used in its installation and is fully insulated when installed such that there are no exposed live parts. This is a particularly important safety feature because it ensures that the electrified terminals cannot inadvertently make electrical contact with the metal portions of the receptacle box in which such receptacles are usually mounted. The receptacle of this invention is constructed such that it can be used with conductors varying in size over a relatively wide range and, moreover, the receptacle is reusable and can be rewired repeatedly. The general size and manner of use of the instant receptacle is similar to that of a conventional screw-terminal receptacle, to minimize the chance of improper installation due to unfamiliarity. Additionally, a portion of the conductor on both sides of the contact terminal is provided with a measure of strain relief. This is an important feature because the receptacle must be pushed back into its wall box after connection is made between the contact terminals and conductors, and this movement may cause the conductors to loosen in their associated contact terminals leading to electrical failures.
A receptacle forming a specific embodiment of the invention is made up of two molded components composed of suitable polymeric compositions and several stamped sheet metal components, and is assembled with the help of standard assembly screws. One of the plastic components is a receptacle body which may be composed of a thermosetting or a thermoplastic compound, such as nylon, and the other is a receptacle front cover having two side covers hinged thereto by respective integral web hinges. A pair of terminal members each having power contacts and power insulation-displacement (or insulation penetrating) terminals are inserted into the receptacle body. A metal yoke, with a metal piece having ground contacts and an insulation displacing ground terminal secured to the yoke, is mounted on the receptacle body such that the rearward part of the yoke cradles the receptacle body. The yoke has several frontwardly-extending yoke projections which are received with interference fits in slots formed in the underside of the receptacle front cover. The yoke projections engaging the walls of the slots serve as the principal connective means for joining the receptacle body to the front cover. The ground contacts and a wall plate screw tab also extend through a suitable pocket in the receptacle body.
The insulation-covered ends of power and ground wires are placed opposite their respective terminal slots, which face outwardly from two sides of the receptacle body, and the side covers are pivoted toward the receptacle body to push the conductors into the slots, displacing portions of the insulation coverings in the process to make electrical connections therebetween. The side covers are secured by way of suitable assembly screws, which when tightened, help ensure that good electrical connections are maintained between the conductors and their respective terminal slots. The side covers are constructed to grip the insulation coverings of wires so as to provide strain relief for the wire terminations. More detailed aspects of the invention will become apparent from the detailed description below.